This application claims priority to German Patent Application No. 100 52 069.3 filed Oct. 19, 2000, which application is herein expressly incorporated by reference.
The present invention relates to a device for measuring torque in a drive assembly.
In order to measure torque at a rotating component, for instance at a torque-loaded driveshaft in a gearbox, preferably strain gauges are applied to the driveshaft. The electric signals generated by the gauges are transmitted by slip ring transmitters to the outside. In such devices, it is possible to generate high-precision torque signals like those required for measuring devices used in laboratories. The signals can also be transmitted in a contact-free way by transmitters and receivers. To provide measuring bridges from strain gauges, to calibrate the gauges and to connect the necessary cables, generates high costs. Also, there is a considerable cost to transmit the signals from the rotating shaft to the stationary components. Furthermore, the error quota is very high as a result of the high degree of integration of electronic components in gearboxes. For many facilities and machines, such a high degree of accuracy of measuring devices is not required. However, the above-mentioned devices cannot be de-refined to provide adequate cost savings. This is the reason why, in spite of the high degree of benefit derived from torque measurements for the respective operating process, such devices are practically never used in drive systems for agricultural machinery. One example of integrating such a device is a gearbox, which is disclosed in DE 42 31 412 C1.
It is an object of the invention to propose a device for measuring torque in a drive assembly. The device has a simple design and is inexpensive. The device does not require electric signals to be transmitted from a rotating component to a stationary receiver.
In accordance with the invention, the device for measuring torque in a drive assembly, comprises a torsion element. The torsion element is rotatingly drivable around a rotation axis in order to transmit torque. Also, the torsion element can be torque loaded.
A reference element rotates with the torsion element. The reference element is torque-free for the torque range to be measured. A first transmitter element is attached to the torsion element. The first transmitter is moved on a rotational circle when the torsion element rotates. A second transmitter element is attached to the reference element. The second transmitter is movable on the rotational circle so as to be circumferentially offset relative to the first transmitter element. A sensor element is stationary relative to the torsion element and the reference element. The sensor element is positioned opposite the rotational circle of the two transmitter elements. The sensor element records the passage of the transmitter elements or reference edges or reference faces of the transmitter elements and generates a corresponding signal. An evaluation unit receives the signals. The evaluation unit determines the respective torque value from an offset of the signals. The reference element participates in the transmission of torque once a predetermined torque value has been reached.
An advantage of this design is that the relative position of the two transmitter elements relative to one another, i.e. the size of the offset between said two elements on the rotational circle, contains information on the value of the torque applied. This information can be derived from signals generated by two transmitter elements when passing the stationary sensor. The sequence of the signals in terms of time, their relative displacement in terms of time, is proportional to the torque applied. The signals can be converted in an evaluation unit into measured torque values. The torque values may be used to generate either a warning signal or an indication or they can be used for controlling the drive. For instance, under certain circumstances, a driven unit may be stopped. On the other hand, depending on the torque value identified, a function of the device such as a higher or lower rotational speed of the driveline provided with the torque measuring device may be controlled. But other functions can also be influenced. Examples for the application of such a torque measuring device are spreading devices for artificial fertilizer or dung. For example, if the torque has dropped to a minimum value in a spreader of artificial fertilizer, this may indicate that the storage container is empty or that the spreading device is no longer adequately supplied with artificial fertilizer. Too high a torque value, a value reaching its maximum, may be an indication of blockages. The participation in the transmission of torque on the part of the reference element from a certain torque value onwards is particularly advantageous if the inventive device is used in agricultural implements. One example is to free an implement when blockages occur. The load is higher than under normal operating conditions. This means that the torque measuring device can be designed such that measurements are only taken within the actual operating range.
In the case of a dung spreading implement, the torque measuring device can be incorporated into the driveline of the working tools which spread the dung onto the field. Also, depending on the measured torque value, it is possible to control the scraper base in order to supply the ejection elements with more or less dung to provide a uniform distribution.
To improve the solution in accordance with the invention, the torsion element includes a torque shaft. The torque shaft includes a first shaft end and a second shaft end. The reference element includes a tube with a first tube end and a second tube end. The reference element is arranged co-axially around the torsion element. The first tube end is firmly connected to the first shaft end. The second transmitter element is arranged at an outer circumference of the second tube end. The second tube end has a recess to enable passage of the first transmitter element attached to the torsional element. Both transmitter elements are arranged in a common plane on the common rotational circle. Thus, this provides a particularly simple design.
According to a further embodiment, a first recess is provided in the second tube end of the reference element which enhances the ability of the reference element to participate in the transmission of torque when a predetermined torque value has been reached. A second recess is diametrically opposed relative to the first recess. Both recesses are each delimited in the circumferential direction by spaced planar stop faces. The first transmitter element is journal-shaped and attached to the torsion element. The first transmitter extends transversely to the rotational axis. The first transmitter, via a first projection, extends radially into the first recess. Further, the first transmitter, via a second projection, projects radially from the second recess. The projecting portion of the first transmitter serves as a transmitter portion. To keep the load low, the two projections are provided with flattened portions. The flattened portions are intended to come to rest against the stop faces of the reference element.
In a preferred embodiment, the second transmitter element includes a journal element. The journal element is arranged on an outer face of the reference element. Thus, the journal element is circumferentially offset relative to the second recess where the second projection emerges. The journal element serves as the second transmitter element. The journal element, with respect of its shape, is preferably designed to correspond to the second projection which serves as the first transmitter element.
The sensor element is associated with a stationary housing. The housing encloses the torsion element and the reference element in the region of the two transmitter elements. The evaluation unit can be arranged, for example, in a region which is visible or noticeable by the tractor driver. Alternatively, it is possible for the evaluation unit to be arranged near the sensor. Accordingly, the signals are transmitted to an indicator or signal unit attached in a region where the tractor driver can see or hear the indicator.
From the following detailed description, taken in conjunction with the drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.